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Summary: Technical film aimed at aircraft crew, focusing on IFF (Identification Friend or Foe), a radio frequency installed in aircraft signalling to a ground station that it is not an enemy aircraft.
Description: The film features an IFF device installed in a Sunderland flying boat. Operating on the CH 1 (Chain Home), CH 2 and GL (gun-laying) bands, every twelve seconds the transceiver tunes itself to a CH ground radar station which receives the pulse, amplifies and returns it to the aircraft. This cycle is repeated while the aircraft is within the frequency range. The procedure is observed on a cathode ray tube display as a series of twelve second downward pulses. At times the pulses may be weak and difficult to interpret. The film features several examples of their actual trace on a CRT display, and their interpretation with the aid of schematic diagrams. A particularly nasty effect occurs when a whole series of twelve second pulses are spread out along the timebase (known as squiter) and can only be resolved by the station Filter Officer adjusting the aircraft’s IFF set. The value of viewing the CRT display through colour optical filters to minimise interference is demonstrated.
Production Country: GB
Production Details: Telecommunications Research Establishment (Production sponsor)
British Thomson-Houston (Production sponsor)